I. Yu. Tolstikhina

Target density effects in collisions of fast ions with solid targets

The influence of the target density on the charge-changing—ionization and electron capture—cross sections when fast ions penetrate through solid targets is considered. It is shown that, with the target density increasing, electron-capture cross sections decrease and ionization cross sections increase, resulting in a higher mean charge of exit ions after a solid target compared to a gas target (often called gas-solid or density effects).Recent experimental data on equilibrium charge-state fractions F∞q of 6.0 MeV u−1 ions with atomic numbers Z = 6–26 passing through carbon foils [10, 11] are described in terms of the calculated charge-changing cross sections using a four-charge state model. It is found that the reasonable agreement can be obtained provided the target-density effects are properly accounted for. Moreover, the present treatment allows one, for the first time, to estimate the distributions of the exit ions over excited nl states from experimental equilibrium charge-state fractions using the charge-changing cross sections calculated with the density effects included; here n and l denote the principal and orbital quantum numbers, respectively.Numerical calculations of the charge-changing cross sections and equilibrium charge-state fractions of exit ions are performed for 6.0 MeV u−1 C2+, Ne4+, Mg5+, Si5+, Ar8+ and Fe9+ ions penetrating through carbon foils. Taking the target-density effects into consideration and comparing the calculated equilibrium charge fractions with the recently observed data for carbon foils, the nl distributions of exit ions with the largest fractions are estimated by fitting the calculated F∞q values to the experimental ones.

EUV spectroscopy of plasmas created in the final anode-cathode gap of the Z-Machine high-current pulsed generator (SNL)

The effect of short-circuit across the final anode-cathode gap of powerful pulsed current generators could hamper efficient power delivery to the Z-pinch plasma. To study this effect, a novel EUV diagnostics of plasmas created in the final section of the transmission line (the anode-cathode gap near the main load) of the Z-Machine high-current generator (Sandia National Laboratories, United States) was developed. The work included developing spectroscopic instruments, theoretical and experimental studies of EUV spectra of iron ions in well-diagnosed laser-produced plasmas, and a comparison of these spectra with those of plasmas created in the final anode-cathode gap of the transmission line. The EUV spectra of highly charged Fe ions in the spectral range λ ∼ 20–800 Å were investigated. In experiments performed at Sandia National Laboratories, spectra of FeXIII-FeXVII ions were observed. A comparison of the measured and calculated spectra shows that the electron plasma temperature in the anode-cathode gap is Te ∼ 200 eV.

Extreme vacuum ultraviolet solar spectra obtained during the SPIRIT experiment aboard CORONAS-F: A catalog of lines in the range 280–330 Å

We present a catalog of 100 lines in the wavelength range 280–330 Å detected by the RES-C spectroheliograph in solar active regions and flares during the SPIRIT experiment aboard the CORONAS-F orbital station. We identified 54 lines. The line intensities recorded during the X3.4 (GOES) solar flare of December 28, 2001, are given. The data reduction procedure is discussed.

Solar EUV Spectra Obtained during the SPIRIT Experiment Onboard the CORONAS-F Satellite: A Catalog of Lines in the Range 176-207 ˚ A

We present a catalog of 65 spectral lines in the range 176–207 Å recorded by the RES spectroheliograph in active regions and flares during the SPIRIT experiment onboard the CORONASF satellite. We have identified 51 lines. The relative intensities of lines recorded during the M6.5 (GOES) flare of September 16, 2001, are given. The data processing technique is discussed.

Ionization of heavy ions in relativistic collisions with neutral atoms

The problem of ionization of ions in ion-ion and ion-neutral relativistic collisions is considered. Formulas for ionization cross sections are derived in the Born approximation in terms of the momentum transfer without allowance for magnetic interactions. Using these formulas implemented in the LOSS-R code, the ionization cross sections are calculated for the K shells of neutral atoms colliding with protons and also for 1s and 2p electrons of multiply charged heavy ions (nuclear charge Z = 80−90) colliding with bare nuclei and neutral atoms. The calculation results are compared with experimental data and calculations of other authors.

Radiative heating of thin Al foils by intense extreme ultraviolet radiation

The effect of induced transparency of thin Al foils radiatively heated by intense extreme ultraviolet (EVU) radiation has been observed. The radiation of the plasma of Z-pinches appearing under the compression of tungsten liners at the Angara-5-1 facility has been used as the radiation that heats the Al foil (peak illumination on the foil ~0.55 TW/cm2) and is transmitted through it. The photoabsorption has been studied in the formed aluminum plasma at temperatures of ~10–30 eV in the density range of ~1–20 mg/cm3 in the wavelength range of ~5–24 nm. Absorption lines of Al4+...7+ ions have been identified in the experimental spectrum. In addition, radiative gas-dynamic simulations of the foil heating and expansion have been performed taking into account radiation transfer processes.

Development of the concept of charge-exchange recombination spectroscopy for ITER

Charge-exchange recombination spectroscopy under ITER conditions is numerically simulated using the DINA code. The code allows one to calculate the attenuation of neutral beams in plasma, the intensity of atomic emission and emission from the ions produced by charge exchange with the neutral beam, and the intensity ratio between the emission related to charge exchange and the background continuum plasma emission. The cross sections for atom-ion interactions in plasma are calculated, and the excitation rates of spectral transitions in hydrogen-like impurity ions are determined. The measurement scheme and the main parameters of the spectrometer proposed for charge-exchange recombination diagnostics in ITER are described.

Influence of relativistic effects on electron-loss cross sections of heavy and superheavy ions colliding with neutral atoms

The influence of relativistic effects, such as relativistic interaction and relativistic wave functions, on the electron-loss cross sections of heavy and superheavy atoms and ions (atomic number Z ≳ 92) colliding with neutral atoms is investigated using a newly created RICODE-M computer program. It is found that the use of relativistic wave functions changes the electron-loss cross section values by about 20–30% around the cross-section maximum compared to those calculated with nonrelativistic wave functions. At relativistic energies E ≥ 200 MeV/u, the relativistic interaction between colliding particles leads to a quasiconstant behavior of the loss cross sections σELrel ∼ const, to be compared with the Born asymptotic law σELB ∼ lnE/E.

Electron loss of heavy many-electron ions in relativistic collisions with neutral atoms

Electron-loss processes arising in collisions of heavy many-electron ions (like U28+) with neutral atoms (H, N, Ar) are considered over a wide energy range including relativistic energies. Various computer codes (LOSS, LOSS-R, HERION, and RICODE), created for calculation of the electron-loss cross sections, and their capability are described. Recommended data on the electron-loss cross sections of U28+ ions colliding with H, N, Ar targets and predicted lifetimes of U28+ ion beams in accelerator are given. Calculated electronloss cross sections are compared with available experimental data and other calculations.

X-ray and vacuum-ultraviolet plasma spectroscopy with the use of new focusing multilayer structures

The spectra of a laser plasma in the soft x-ray (0.8–0.95 nm) and vacuum ultraviolet (3–4 nm) ranges are recorded with the use of new focusing multilayer structures. It is demonstrated that the electron temperature of the light-element plasma produced by a laser pulse with an energy of ∼1 mJ can be measured by using the relative intensities of the satellites and the lines of ions with different charges.